Why the moon looks bigger at the horizon

[DaveC426913]

Great, thanks, I'm glad this is over! So is my wife...she thinks I spend too much time on this forum, and looking at the moon, and not enough time helping around the house. And I'll have to admit, she's probably right.

Thanks for your valued input.

It is a calling for me too.


You keep watching those skies Phanthom.

Wherever you go, I'll be there.


I am.

Anti-PhanthomJay.

 

[PhanthomJay]

It is a calling for me too.


You keep watching those skies Phanthom.

Wherever you go, I'll be there.


I am.

Anti-PhanthomJay.

Looks like you'll be back in the running for the 2010 Best Humor Award!

 

[raylphscs]

I still think the illusion theory is wrong. It is aparently the optical lenz effect of the spherical atomsphere acted like a telescope. when the moon is near the horizon, it not only looks big, but you can see much details on its surface like the dark areas and dark spots. If a brain illusion caused the moon seem big, there should be no more details to be seen, only size bigger.
Illusion theory is wrong and is not scientific.

 

[D H]

Read the thread, raylphscs. There is a tiny atmospheric effect near the horizon. This tiny effect does not explain the Moon illusion for two reasons. (1) The effect is tiny. We perceive the Moon to be considerably bigger near the horizon compared to when it is overhead. (2) The atmospheric effect makes the apparent size of the Moon a tiny bit smaller when the Moon is near the horizon.

 

[Brin]

I still think the illusion theory is wrong. It is aparently the optical lenz effect of the spherical atomsphere acted like a telescope. when the moon is near the horizon, it not only looks big, but you can see much details on its surface like the dark areas and dark spots. If a brain illusion caused the moon seem big, there should be no more details to be seen, only size bigger.
Illusion theory is wrong and is not scientific.

Wow. I propose a new rule after reading this entire freakin' thread: Quantitative results. Go get your 'lenz effect of the spherical atmosphere acted like a telescope' equations and get to work. It's not that hard. I think it's like chapter 34 or something in Young and Freedman.

Calculate precisely how large the moon should appear under each of the conditions being proposed. Post them here if they are significantly different (not the 12% we know about already).

 

[JDługosz]

I still think the illusion theory is wrong. It is aparently [sic] the optical lenz effect of the spherical atomsphere [sic] acted like a telescope. when the moon is near the horizon, it not only looks big, but you can see much details on its surface like the dark areas and dark spots. If a brain illusion caused the moon seem big, there should be no more details to be seen, only size bigger.
Illusion theory is wrong and is not scientific.

Wrong, wrong, and wrong. The illusion theory is scientific because the actual angular size can be measured with scientific instruments. It is actually a tiny bit smaller at the horizon, so appearing larger is an illusion. I for one don't see more details when it is low, other than the phycological effect of being able to look at it for a while rather than just glance at it. If you stare at the high moon for a bit, it will seem to "expand" in your attention to fill your gaze. A low red moon might have different contrast than a high white moon. If you calculate the effect you site, you'll find it does not match your assertions.

 

[raylphscs]

Same angular size behind different lenz, meaning different image size! This was what the illusion theory ignored.! The so called experiments forgot the fact that there are different lenz between the moon and the observer when the moon is at different altitude. ! Why people don't consider everything involved when doing experiment? So end up with erroneous conclusion?
when we see objects on the other side of a lenz, the image looks different size if the lenz change shape, this is scientific, it is not illusion, it is the light rays bent causing the image size change. It is not any illusion causing the horizontal moon looks big. The moon image size change is because the atomosperic lenz shape changed between the moon and observer when the moon change altitude. If there were no atomasphere on earth, the moon image would never change size no matter on the horizon or above our head!

 

[Brin]

I'm guessing you haven't heard of "spherical symmetry?"

Seriously. Get a pad of paper, and draw the LENS. Show us the difference!

 

[DaveC426913]

Same angular size behind different lenz, meaning different image size! This was what the illusion theory ignored.! The so called experiments forgot the fact that there are different lenz between the moon and the observer when the moon is at different altitude. ! Why people don't consider everything involved when doing experiment? So end up with erroneous conclusion?
when we see objects on the other side of a lenz, the image looks different size if the lenz change shape, this is scientific, it is not illusion, it is the light rays bent causing the image size change. It is not any illusion causing the horizontal moon looks big. The moon image size change is because the atomosperic lenz shape changed between the moon and observer when the moon change altitude. If there were no atomasphere on earth, the moon image would never change size no matter on the horizon or above our head!

raylphscs, you have not thought this through. As previously pointed out, the effect of atmospheric lensing will actually serve to decrease the apparent diameter of the Moon.

And please stop screaming about being scienitific. The only one not being scientific here is you. You've got an idea stuck in your head that you haven't examined and won't let go of.

 

[raylphscs]

I'm guessing you haven't heard of "spherical symmetry?"

the atomasphere is symetrical to the center of the earth, but you are on the surface of the earth, it is not spherically symetrical to you. you are too far away from the center of the earth.

 

[rustynail]

@raylphscs:

You know that the moon revolves around the earth, and does not actually "change altitude", right?

 

[Brin]

the atomasphere is symetrical to the center of the earth, but you are on the surface of the earth, it is not spherically symetrical to you. you are too far away from the center of the earth.

Draw a picture, do the numbers. Read the thread. I'm done here.

 

[raylphscs]

As previously pointed out, the effect of atmospheric lensing will actually serve to decrease the apparent diameter of the Moon.

This was wrong, you pointed out doesn't mean it be the truth. while the moon near the horizon, the atomsphere lenz serves to enlarge the image. while it is above head, the atomosphere lenz changed shape and causing different image size.

 

[raylphscs]

As previously pointed out, the effect of atmospheric lensing will actually serve to decrease the apparent diameter of the Moon.

This was wrong, you pointed out doesn't mean it be the truth. while the moon near the horizon, the atomsphere lenz serves to enlarge the image. while it is above head, the atomosphere lenz changed shape and will decrease the image size.C:\Users\owner\Documents\moon_earth_atomosphere.jpg

 

[raylphscs]

@raylphscs:

You know that the moon revolves around the earth, and does not actually "change altitude", right?

By "altitude" I mean how close to the horizon, don't go by the literal meaning please

 

[rustynail]

By "altitude" I mean how close to the horizon, don't go by the literal meaning please

Using correct words along with their correct acception just seems to be a good way to be understood. But just because I pointed out doesn't mean it be the truth...

 

[raylphscs]

QUOTE=Brin;2959610]Golly gee, you're thick.
Draw a picture, do the numbers. Read the thread. I'm done here.[/QUOTE]

please the analogy picture

[

 

[D H]

Your picture doesn't show your purported atmospheric effect. It cannot for the simple reason that your purported effect doesn't exist. The atmosphere does not act as a lens that magnifies the size of the Moon.

Aside: The word is lens, not lenz. Most browsers have spell checkers and highlight misspelled words. Mine, for example, shows "lenz" with a red underscore. That means that "lenz" is not a word.

Back on topic: Using the well-known equation 1 picture = 1000 words, here is a several thousand word essay on this topic:

Source: http://antwrp.gsfc.nasa.gov/apod/ap020130.html

Source: http://spaceweather.com/submissions/large_image_popup.php?image_name=Chris-Picking-moon_rising_composite_1213915516.jpg
[PLAIN]http://spaceweather.com/submissions/pics/c/Chris-Picking-moon_rising_composite_1213915516_med.jpg

Source: http://greenmanblog.com/archives/P87.html
http://greenmanblog.com/uploads/FullMoons.jpg

Source: http://epod.usra.edu/blog/2007/06/rising-moon-illusion.html
[URL]http://epod.typepad.com/.a/6a0105371bb32c970b011571a50254970b-600wi[/URL]

 

[sophiecentaur]

Smashing pictures! And they should be proof enough for anyone.

I haven't trawled the whole way through this thread but I always thought that the reason was almost totally subjective. The brain does its best to estimate things but often does a pretty poor job. Out on its own, the moon is just an unimportant blob of light and the brain doesn't give it much significance. When you see it going down behind a massive building, tree or hill, you realize just how big it is in context.

You get a similar effect when looking up at the top of a ladder from the ground and then looking at the ground from the top of the ladder. I reckon at least two to one subjective difference! I never get vertigo looking up at a ladder. Context is everything.

Of course, the Moon's distance varies significantly over the year and it sometimes really does subtend a bit 'bigger' angle at times. That's not an illusion.

 

[DaveC426913]

please the analogy picture

[

OK, now show how it leads to the effect you describe.

 

[JDługosz]

You get a similar effect with traffic lights. If you see one on the ground with people working on it, it seems much larger than you expected. They can be as tall as a man, so 5 or 6 feet. But in their normal location they seem small.

 

[DaveC426913]

You get a similar effect with traffic lights. If you see one on the ground with people working on it, it seems much larger than you expected. They can be as tall as a man, so 5 or 6 feet. But in their normal location they seem small.

Huh. Never thought of that. Cool.

 

[txd453]

I'm just curious, I've never tried this or heard of it being used, but... is it possible to use a micrometer or a set of calipers (dial calipers for example) held a set distance from the observer's eye, to make size estimates? Would that be a more quantitative way of doing it, rather than using a dime or a pencil eraser?

 

[DaveC426913]

I'm just curious, I've never tried this or heard of it being used, but... is it possible to use a micrometer or a set of calipers (dial calipers for example) held a set distance from the observer's eye, to make size estimates? Would that be a more quantitative way of doing it, rather than using a dime or a pencil eraser?

Uh. Sure.

Why?

Do you doubt the likelihood that the effect is as mentioned? Do you question the pictures above?

 

[pallidin]

You get a similar effect with traffic lights. If you see one on the ground with people working on it, it seems much larger than you expected. They can be as tall as a man, so 5 or 6 feet. But in their normal location they seem small.

Uh, a standard traffic light is about 41 inches tall. Just a little over 3-feet.

Source: http://answers.yahoo.com/question/index?qid=20070322180304AArkOTp

 

[D H]

Uh, a standard traffic light is about 41 inches tall. Just a little over 3-feet.

Source: http://answers.yahoo.com/question/index?qid=20070322180304AArkOTp

Gotta love those bad answers at answers.yahoo.com!

That 41 inch figure is not the "standard traffic light" size. That size is the size of an older traffic light used at the intersection of two low-speed roads. Those signals use 8 inch diameter signal lenses. Traffic light lenses in the US come in two sizes: 8 inch (200 mm) and 12 inch (300 mm). Those older 8 inch diameter lights are being phased out. Those 12 inch diameter signal lights are the mandated size for new vehicular traffic signals except at the intersection of two small low-speed road (Manual on Uniform Traffic Control Devices, section 4D.07).

Some traffic signals have a vertical stack of five lights, the standard red/yellow/green plus two more for protected turn lanes. At 14 inches per light plus 8 inches top and bottom, those signals are over 7 feet tall. A simple three light (red/yellow/green) signal with 12 inch diameter lenses is just shy of 5 feet tall.Back to the moon illusion discussion ...

 

[Redbelly98]

Back to the moon illusion discussion ...

No! Pleeeease, anything but that!

I'm just curious, I've never tried this or heard of it being used, but... is it possible to use a micrometer or a set of calipers (dial calipers for example) held a set distance from the observer's eye, to make size estimates? Would that be a more quantitative way of doing it, rather than using a dime or a pencil eraser?

Yes, certainly. Just be careful about holding the calipers the same distance away for both measurements, which would be done several hours apart.

Uh. Sure.

Why?

Do you doubt the likelihood that the effect is as mentioned? Do you question the pictures above?

But questioning, and verifying with measurement, is how science gets done. Whether it's researchers on the cutting edge, or students and nonprofessionals trying to learn what is already known by professionals.

 

[sophiecentaur]

But questioning, and verifying with measurement, is how science gets done. Whether it's researchers on the cutting edge, or students and nonprofessionals trying to learn what is already known by professionals.

True but your alternative measurement needs to be valid. What you describe, on its own, may well not be.

Edit - I'm not sure who I am replying to, actually but my point stands.

 

[sophiecentaur]

I still think it's amazing that a piece of green cheese can look so different as it moves around the sky.

 

[pallidin]

My bad, DH, thanks for the clarification.

 

[txd453]

I'm just curious, I've never tried this or heard of it being used, but... is it possible to use a micrometer or a set of calipers (dial calipers for example) held a set distance from the observer's eye, to make size estimates? Would that be a more quantitative way of doing it, rather than using a dime or a pencil eraser?

Uh. Sure.

Why?

Do you doubt the likelihood that the effect is as mentioned? Do you question the pictures above?

True but your alternative measurement needs to be valid. What you describe, on its own, may well not be.

Edit - I'm not sure who I am replying to, actually but my point stands.

Maaan, y'all are a touchy bunch! :=) The statement prior to the question was literal, I'm just curious; and the photos are definitive. However, I don't see how the 'alternative measurement' would be less valid than using a dime or a pencil eraser. What would be the sources of error? It should be fairly easy to rig something to reduce the variability in the distance between the calipers and the observer's eye...

 

[D H]

A pencil eraser would work just fine for this, maybe a grease pencil if you have long arms.

A dime will work if you want something more precise. You will need some device to hold the dime about 2 meters away from your eyes however.

 

[DaveC426913]

Maaan, y'all are a touchy bunch! :=)

That's the way we roll here. You want the Wishy Washy Forum of Fluffy Guesses, that's next door.

 

[MagnetDave]

Can we enshrine this thread in the Cranial Density Hall of Fame?

Any time we are discussing something sophisticated with someone who refuses to understand, can we just say cite the Moon Principle: No evidence can be so irrefutable as to overcome all desire to not be wrong? Sort of a scientific Godwin's Law, when the argument has been explained with the maximum possible clarity, therefore consuming all value in the discussion...

Agree?

 

[DaveC426913]

I feel strangely attracted to you...